Adjustable strength permanent magnet



A118. 1949- R. G. JEWELL 2,479,363

ADJUSTABLE STRENGTH PERMANENTMAGNET Original Filed Dec. 12, 1942 Ihvehtor: Richard 6. Jewell,

y WW His Attc arhey- PM Aug. 1c, 1949 2.47.93! ADJUSTABLE STRENGTH PERMANENT MAGNET Richard G. Jewell, Sworn to General Electric New York Com pccott, Masa, assignmpony, a corporation of Original application December 12, 1942, Serial No. 468,859. Divided and this application January 15, 1946, Serial No. 841,317

2 Claims. (Cl. 175-21) My invention relates to an adjustable strength permanent magnet of the character described in my Patent No. 2,418,032, March 25, 1947, oi. which the present application is a division. The invention is described as applied to the erecting device of a gyroscope, although it is of general application.

The features of my invention which are believed to be novel and pa'tentable will be pointed out in the claims appended hereto. For a better understanding of my invention, reference is made in the following description to the accompanying drawing in which Fig. 1 represents a cross-sectional view of one form of my adiustable strength permanent magnet as used in an erecting device for gyroscopes. Fig. 2 is a plan view of the magnet of Fig. 1, and Fig. 3 is a perspective view of an adjustable permanent magnet plug used in the magnet of Figs. 1 and 2.

In Figs. 1 and 2 there is shown a permanent magnet of a form used in the erecting device of a gyroscope. The magnet is formed from a hollow cylinder with diametrical slots I and 2 at right angles to each other, dividing one end of the cylinder into four equal triangular-shaped sectors 3, l, 5, and 6. These slots extend roughly two-thirds the length of the cylinder, so that the sectors are joined at the base with the yoke section 1. In the form of magnet shown there is a circular axial opening 8 through the yoke, which opening is in line with or defines the inner surface of the four sectors.

The structure is formed of permanent magnet material and is polarized, so that the four sectors are alternately polarized as indicated in Fig. 2, such polarization being desirable for the use here represented.

The magnet cooperates with a conductor 9. The magnet and conductor are relatively rotatable about a central axis vertical as represented in Fig. 1. The adjacent surfaces of magnet and conductor define an air gap which is generally spherical in shape, and the two parts are subject to relative displacement with respect to the center line. The purpose of the arrangement is to produce eddy current damping action and resulting erecting forces which tend to maintain the two parts centrally disposed relative to each other when there is a departure from such relation. For a more complete description of the structure and operation of a gyro erecting device, reference may be had to the parent application. In such application it is desirable that the permanent magnet strength of the upper surfaces of the four sectors be equal. Also, it is desirable after the magnet has been completed and magnetized and is mounted in operating position on the gyroscope or other device where such adjusting feature is useful.

It will be noted that central radial bore holes ill have been indicated by dotted lines in Figs. 1 and 2 in the four sector-shaped pole pieces of the magnet. Such bore holes are preferably some distance beneath the pole faces but nearer the pole faces than to the yoke ends of the poles. Into each of suchbore holes I insert a plug such as is shown in Fig. 3. The plugs may be slit nearly through their diameters as at H so as to be capable of limited resilient radial contraction and expansion. They may thus be easily inserted in the holes and yet fit tightly and resist displacement or turning. The plugs are also provided with a screwdriver slot I2 in the outer ends, so that they may be turned in their holes after assembly. Such plugs are made of permanent magnet material and are preferably inserted in as desired by turning the corresponding plug or plugs.

original position, strengths are obtained by a lesser angle of turn.

a, whole may also be weakened by turning all of the plugs by the desired amount. I have found that when a plug is first turned degrees from its original position where magnetized and then turned back to such original position, it undergoes a. slight knockdown in its magnetic strength. Hence, it may be desirable to knock down or stabilize all of the plugs after the initial magnetization in this way. Subsequent adjustments will thennot change the magnetic strength of the plugs. Such a magnet may and various intermediate pole netic strength while in test or operating position simply by the use of a small screwdriver.

The form of permanent magnet herein described and illustrated is for a particular purpose. However, the invention is generally applicable to a wide variety of forms of permanent magnet structures, and I aim to cover the same by claims which are commensurate with the scope of the invention. It is, of course, obvious that the hole It in any one or more of the pole pieces may be left empty or filled with a plug of soft iron to obtain further variations in the strength of the permanent magnet structures as a whole.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A permanent magnet structure comprising a hollow cylindrical structure or permanent magnet material which has axial slots across its diameter at right angles to each other extending approximately two-thirds the length of the cylinder from one end to form four symmetrically arranged approximately triangular-shaped pole pieces joined by the unslotted part of the cylinder as a yoke, said structure being permanently magnetized to produce a four-pole permanent magnet wherein the four pole pieces have alternate polarity, and means comprising permanent magnet plug insert portions of said pole pieces rotatable about an axis at right angles to the flux axis of said pole pieces for adjusting the relative strength of said pole pieces after being magnetized.

; have its several poles exactly balanced as to mafl- I 2. A, permanent magnet structure having an even number of axially extending pole pieces symmetrically arranged in a circle and alternately polarized, including supporting structure interconnecting said pole pieces for securing them in such relation, and means for adjusting the relative permanent magnet strength of said pole pieces comprising rotatively mounted permanent magnet plug inserts in at least someoi' said pole pieces, the plug inserts extending transversely of the flux axis of said pole pieces'and so magnetized that their fluxes may be added to or subtracted from the fiux of the corresponding REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 204,141 Eaton May 28, 1878 1,906,027 Wahl Apr. 25, 1933 1,987,144 Dinkel Jan. 8, 1935 2,268,011 Beechlyn Dec. 30,1941 2,287,286 Bing et al June 23, 1943 2,435,735 Briggs Feb. 10, 1948 FOREIGN Number Country Date 442,442 Great Britain Feb. 7, 1936 488,875 Great Britain July 15, 1938 

